Hi All,
I started to test these new and recent components for me: Hall effect sensors and tunnel magnetoresistances.
They are used in industry for magnetic field detection.
I tested the SS496A and TMR2005 in a basic setup, to familiarize myself with how they react, and especially to get a practical idea about their sensitivity.
The
SS496A (3 pins) is powered by a voltage V in the range of 4 to 7V, and the transverse Hall output voltage related to the deviation of electrons by the magnetic field is amplified and presented on the third pin.
Taking the mid-point of the power supply as a reference, the output varies from 0 to ±V/2 depending on the direction and intensity of the magnetic field. I made the middle point thanks to a simple resistance network with a multi-turn potentiometer. The voltmeter is connected between this mid-point and the output (see diagram). I used an HP3468A multimeter, which allows me to see µV.
The
TMR2005 (4 pins) consists of a bridge of 4 magnetoresistances mounted in such a way that by circulating a current between two opposite nodes, the voltage between the other two opposite nodes that constitute the output varies according to the magnetic field. The most difficult thing was to solder the wires (component size <3 mm, see photo)! A magnifying glass is essential.
Note that the background noise is not negligible, I think there is noise in 1/f, and there is also the 50 Hz component of the mains current here whose magnetic field is everywhere. I have improved things a little by using a 4.5 V battery instead of my mains power supply, but it is still far from enough. The voltage of the voltmeter fluctuates by 50 to 200 µV.
Result in static:
I used a stack of 5 rectangular neodymium magnets of 50x20x2mm, and observed the output voltage as I turned them over at some distance, to reverse the polarity felt by the sensor.
At a distance of 2 meter, the output voltage of the SS496A varies by about 100µV, this is perfectly visible. At 3 meters, we no longer distinguish the useful signal from the background noise.
With the TMR2005, the sensitivity is much better, I have the same signal at 3 m as I had with the Hall effect sensor at 2 m. At 4 m, the signal is still slightly visible. And the TMR2005 is not the most sensitive of the two magnetoresistances I bought! I'll have to test the TMR2104.
These components are therefore extremely sensitive. I improved the range a little by sandwiching the SS496A between 2 ferrite rods in line.
Result in dynamics:
With a variable field, how do they react? This is a disaster. I used a 16 cm diameter coil, 100 turns, powered by a sine signal. Above 500 Hz, we begin to see the decrease of the signal. At 10 Khz, the signal disappears in the background noise, both with the SS496A and the TMR2005. Don't expect them to react to the electromagnetic field of a radio wave!
Why these tests?
In particular, the analysis of the Marinov device shows that a spatial gradient of the vector potential should be at the origin of a force on moving electrons. This force should have an effect similar to the Lorentz force, but without a magnetic field, including on the electrons of a Hall effect sensor. Hence the idea of using this type of sensor to avoid the mechanical problems we have with Marinov (but there are others, like the B field leak, that's the problem I'm on now). This is the first step.
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Topic: En route for the detection of a force from the vector potential (Read 11359 times)
